1. Field of the Invention
The present invention relates to an apparatus and a method of separating a sample and a substrate fabrication method and, more particularly, to an apparatus and a method of separating a sample having an internal fragile structure and a substrate fabrication method using the separating apparatus.
2. Description of the Related Art
A substrate (SOI substrate) having an SOI (Silicon On Insulator) structure is known as a substrate having a single-crystal Si layer on an insulating layer. A device using this SOI substrate has many advantages that cannot be achieved by ordinary Si substrates. Examples of the advantages are as follows.
(1) The integration degree can be increased because dielectric separation is easy.
(2) The radiation resistance can be increased.
(3) The operating speed of the device can be increased because the stray capacitance is small.
(4) No well step is necessary.
(5) Latch-up can be prevented.
(6) A completely depleted field-effect transistor can be formed by thin film formation.
Since an SOI structure has the above various advantages, researches have been made on its formation method for these several decades.
As one SOI technology, an SOS (Silicon On Sapphire) technology by which Si is heteroepitaxially grown on a single-crystal sapphire substrate by CVD (Chemical Vapor Deposition) has been known for a long time. This SOS technology was recognized temporarily as the most matured SOI technology. However, the SOS technology has not been put into practical use to date because, e.g., a large amount of crystal defects are produced by lattice mismatch in the interface between the Si layer and the underlying sapphire substrate, aluminum that forms the sapphire substrate mixes in the Si layer, the substrate is expensive, and it is difficult to obtain a large area.
A SIMOX (Separation by ion IMplanted OXygen) technology appeared following the SOS technology. Various methods of this SIMOX technology have been attempted to, e.g., reduce the crystal defects and the fabrication cost. Examples are a method of forming a buried oxide layer by implanting oxygen ions into a substrate, and a method of bonding two wafers with an oxide film sandwiched between them and leaving a thin single-crystal Si layer behind on the oxide film by polishing or etching one of the wafers. Another example is a method in which hydrogen ions are implanted to a predetermined depth from the surface of an Si substrate on which an oxide film is formed, the resultant substrate is bonded to another substrate, and the other substrate is peeled by a heat treatment or the like such that a thin single-crystal Si layer is left behind on the oxide film.
A new SOI technology is disclosed in Japanese Patent Laid-Open No. 5-21338. In this technology, a first substrate obtained by forming a non-porous single-crystal layer on a single-crystal semiconductor substrate having a porous layer is bonded to a second substrate via an insulating layer (SiO2), and the two substrates are separated from the porous layer to transfer the non-porous single-crystal layer to the second substrate. This technology is advantageous in that the SOI layer has high film thickness uniformity, the crystal defect density in the SOI layer can be decreased, the SOI layer has high surface flatness, no expensive special fabrication apparatus is necessary, and SOI substrates having SOI films about a few hundred xc3x85 to 10 xcexcm thick can be fabricated by the same fabrication apparatus.
In addition, Another technology is disclosed in Japanese Patent Laid-Open No. 7-302889 in which, after the first and second substrates described above are bonded, the first substrate is separated from the second substrate without being broken, and the separated first substrate is reused by smoothening the surface and again forming a porous layer. Since the first substrate can be economically used, this technology has the advantages that the fabrication cost can be largely reduced and the fabrication process is also simple.
In the above technologies, however, when the two bonded substrates are separated it is necessary to prevent damages to the substrates and protect the fabrication apparatus and the like from contamination caused by the generation of particles.
The present invention has been made in consideration of the above situation and has as its object to provide an apparatus and a method suited to separate a sample such as a substrate, parts constituting the separating apparatus, and a substrate fabrication method using the separating apparatus.
A sample separating apparatus according to the present invention is a separating apparatus for separating a sample having an internal fragile structure, characterized by comprising a jet unit for ejecting a jet of liquid or gas, and a guide unit for concentrating the jet of liquid or gas ejected from the jet unit into the fragile structure of the sample, wherein the sample is separated from the fragile structure.
In the above separating apparatus, the guide unit preferably concentrates the jet of liquid or gas ejected from the jet unit into the fragile structure of the sample by decreasing a width of the jet to a predetermined width.
In the above separating apparatus, it is preferable that the guide unit have a hole for decreasing the width of the jet of liquid or gas ejected from the jet unit, and a width of an entrance of the hole be larger than the width of the jet of liquid or gas ejected from the jet unit.
In the above separating apparatus, it is preferable that the sample to be separated have a groove recessed toward an externally exposed portion of the fragile structure, and a width of an exit of the hole be smaller than a width of the groove.
In the above separating apparatus, the sample to be separated preferably has a groove recessed toward an externally exposed portion of the fragile structure.
In the above separating apparatus, the groove preferably has a substantially V-shaped section.
The above separating apparatus preferably further comprises an adjusting mechanism for adjusting a positional relationship between the guide unit and the sample.
In the above separating apparatus, the adjusting mechanism preferably adjusts the positional relationship between the guide unit and the sample by moving the guide unit.
It is preferable that the above separating apparatus further comprise an adjusting mechanism for adjusting a positional relationship between the guide unit and the sample, and the adjusting unit adjust the positional relationship between the guide unit and the sample to concentrate the jet of liquid or gas ejected through the guide unit into the groove.
In the above separating apparatus, the adjusting mechanism preferably adjusts the positional relationship between the guide unit and the sample by moving the guide unit.
The above separating apparatus preferably further comprises a support mechanism for supporting the sample.
In the above separating apparatus, it is preferable that the fragile structure of the sample to be separated form a substantially flat plane, and the support mechanism support the sample to send the jet of liquid or gas ejected through the guide unit in a direction of the plane of the fragile structure.
In the above separating apparatus, it is preferable that the support mechanism comprise a rotating mechanism for rotating the sample around a shaft disposed in a direction substantially perpendicular to the plane of the fragile structure, and support the sample while rotating the sample.
In the above separating apparatus, the guide unit is preferably disposed in a support unit for supporting the sample.
In the above separating apparatus, it is preferable that the support unit comprise two holding units for holding the sample by clamping the sample from both sides, and the guide unit be formed by a gap between opposing portions of the two holding units.
In the above separating apparatus, it is preferable that inclined surfaces be formed in the opposing portions of the two holding units, and the opposing inclined surfaces concentrate the jet of liquid or gas ejected from the jet unit into the fragile structure of the sample by decreasing the width of the jet to a predetermined width.
In the above separating apparatus, it is preferable that the sample to be separated have a disk-like shape, the opposing portions of the two holding units form annular rims, and the sample be held inside the rims.
In the above separating apparatus, the holding units preferably hold the sample to warp the sample by a pressure of liquid or gas.
In the above separating apparatus, the support mechanism preferably comprises a holding unit for holding substrate as a sample to be separated.
In the above separating apparatus, the two holding units are preferably holding units for holding a substrate as a sample to be separated.
In the above separating apparatus, the substrate preferably has a porous layer as a fragile structure.
A guide apparatus according to the present invention is a liquid or gas guide apparatus to be applied to a method of separating a sample having an internal fragile structure by ejecting a jet of liquid or gas, characterized by comprising a guide unit for concentrating the jet of liquid or gas ejected from a jet unit into the fragile structure of the sample.
In the above guide apparatus, the guide unit preferably concentrates the jet of liquid or gas ejected from the jet unit into the fragile structure of the sample by decreasing a width of the jet to a predetermined width.
In the above guide apparatus, it is preferable that the guide unit have a hole for decreasing the width of the jet of liquid or gas ejected from the jet unit, and a width of an entrance of the hole be larger than the width of the jet of liquid or gas ejected from the jet unit.
In the above guide apparatus, it is preferable that the sample to be separated have a groove recessed toward an externally exposed portion of the fragile structure, and a width of an exit of the hole be smaller than a width of the groove.
In the above guide apparatus, the sample to be separated preferably has a groove recessed toward an externally exposed portion of the fragile structure.
In the above inducting apparatus, the groove preferably has a substantially V-shaped section.
The above guide apparatus preferably further comprises a connecting unit for connecting with a sample separating apparatus comprising the jet unit and a holding mechanism for holding the sample, and an adjusting mechanism for adjusting a positional relationship between the guide unit and the sample.
A sample support apparatus according to the present invention is a sample support apparatus to be applied to a method of separating a sample having an internal fragile structure by ejecting a jet of liquid or gas, characterized by comprising two holding units for holding the sample by clamping the sample from both sides, wherein a guide unit for concentrating a jet of liquid or gas ejected from a jet unit into the fragile structure of the sample is formed by a gap between opposing portions of the two holding units.
In the above support apparatus, it is preferable that inclined surfaces be formed in the opposing portions of the two holding units, and the opposing inclined surfaces concentrate the jet of liquid or gas ejected from the jet unit into the fragile structure of the sample by decreasing he width of the jet to a predetermined width.
In the above support apparatus, it is preferable that the sample to be separated have a disk-like shape, the opposing portions of the two holding units form annular rims, and the sample be held inside the rims.
In the above support apparatus, the holding units preferably hold the sample to warp the sample by a pressure of liquid or gas.
In the above support apparatus, the sample to be separated preferably has a groove recessed toward an externally exposed portion of the fragile structure.
In the above support apparatus, the groove preferably has a substantially V-shaped section.
In the above support apparatus, a sample to be supported is preferably a substrate.
In the above support apparatus, the substrate preferably has a porous layer as a fragile structure.
A sample separating method according to the present invention is characterized by separating a sample from a fragile structure by using the separating apparatus described above.
In the above separating method, water is preferably used as a liquid to be ejected from the jet unit.
A substrate separating method according to the present invention is a separating method in which a substrate stack fabricated by bonding a non-porous layer of a first substrate, having one surface on which a porous layer and the non-porous layer are sequentially formed, to a second substrate is separated from the porous layer, characterized in that the separating apparatus described above is used in the separation.
A substrate fabrication method according to the present invention is a substrate fabrication method comprising the step of bonding a first substrate, having one surface on which a porous layer and the non-porous layer are sequentially formed, to a second substrate, and the step of separating the bonded substrate stack from the porous layer, characterized in that the separating apparatus described above is used in the separation step.
Another separating apparatus according to the present invention is a separating apparatus for separating a plate-like sample having an internal fragile structure, characterized by comprising a support mechanism for supporting the plate-like sample, and a jet unit for ejecting a jet of liquid or gas upon the fragile structure of the plate-like sample supported by the support mechanism, wherein the support mechanism supports the plate-like sample to warp a periphery of the plate-like sample by a pressure of the liquid or gas injected into the plate-like sample.
Further objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments of the present invention with reference to the accompanying drawings.